1. Field of the Invention
The present invention relates generally to ink cartridges and ink supply systems. In particular, the present invention is directed towards ink cartridges which may be used in combination with ink jet printers, and towards ink supply systems applicable to ink jet printers.
2. Description of Related Art
A known inkjet printer has a recording head from which ink is discharged onto a sheet of paper to form images on the sheet of paper. The known inkjet printer also has a main ink tank, and a sub ink tank mounted on the recording head. The main ink tank and the sub ink tank are in fluid communication with each other via an ink supply path formed by a flexible tube. The known inkjet printer also has an ink supply mechanism such as a positive displacement pump. The pump is provided in the ink supply path between the main ink tank and the sub ink tank and is configured to supply ink from the main ink tank to the sub ink tank. Ink is drawn into the inside of the pump and then is pressurized by the pump to be supplied to the sub ink tank. In some cases, the main ink tank and the pump are disposed in a cartridge, and the cartridge is configured to be removable from the inkjet printer.
Nevertheless, since the pump is provided in the ink supply path, ink may leak from the pump if the pump breaks, the tubing of the pump ages and deteriorates, or the pump sealing deteriorates.
Another known inkjet printer has a recording head from which ink is discharged onto a sheet of paper to form images on the sheet of paper. The known inkjet printer also has an ink tank storing ink therein. The recording head and the ink tank are in fluid communication with each other via an ink supply path formed by a tube. The known inkjet printer also has a pump provided in the ink supply path between the ink tank and the recording head. The pump is configured to supply ink from the ink tank to the recording head and also return ink from the recording head to the ink tank. When ink is returned from the recording head to the ink tank, air bubbles, which may have been trapped in the recording head or the tube, or both, flows into the ink tank. Air bubbles are separated from ink in an ink chamber provided in ink tank. Thus, air bubbles are removed from recording head or the tube, or both.
Yet Another known inkjet printer has an ink tank, and the ink tank has a valve configured to allow and prevent fluid communication between the ink tank and a recording head. The valve is accommodated in a valve accommodating chamber provided in the ink tank.
If the ink tank of the known inkjet printer third described above is applied to the known inkjet printer second described above, ink in the valve accommodating chamber also needs to be returned to the ink chamber as well as ink in the recording head and the tube. This is because, if some of the ink in the recording head and the tube is left in the valve accommodating portion, air bubbles trapped in the ink may adhere to the valve, which may disturb the movement of the valve. Moreover, the air bubbles adhering to the valve may return into the tube and the recording head when ink is supplied from the ink tank to the recording head. Nevertheless, a more powerful pump having relatively high capacity may be more effective in returning ink in the valve accommodating chamber to the ink chamber as well as ink in the recording head and the tube.